Aleutian Low-Beaufort Sea Anticyclone (ALBSA) index, 1940-2025

The Aleutian Low-Beaufort Sea Anticyclone, or "ALBSA", is a daily, 4-point index combining two orthogonal 850 hPa (hectopascal) differences (one meridional, one zonal). Collectively, this captures the variability in the North Pacific/Pacific Arctic tropospheric circulation. The purpose is to track the juxtaposition of the Aleutian Low and Beaufort High pressure centers, specifically the strength/position of the former and the meridional dipole associated with the latter. The utility of the index is its sensitivity to advection events from the North Pacific into the Arctic and how the pattern of circulation steers that advection. It represents the variability of the NPI, and also includes information specific to the advection across Alaska and up through the Bering Strait, and the East Siberian/Chukchi/Beaufort Seas. To date, the index has been used to evaluate interannual variability in the timing of seasonal cryospheric transitions and ecosystem phenology of the North Pacific and Pacific Arctic, as well as subseasonal variability in Bering Sea ice expansion/retreat and aerosol transport events. The first data set in this series was calculated using the ECMWF Reanalysis v5 (ERA5) (see methods) for January 1940 through May 2025. We intend to update the series periodically, approximately annually in June because the index is most useful September through May, to append the most recent year.

阿留申低压-波弗特海反气旋（Aleutian Low-Beaufort Sea Anticyclone，简称ALBSA）是一种每日四点指数，整合了两组正交的850百帕（hectopascal）高度差（一组为经向分量，另一组为纬向分量）。该指数可整体捕捉北太平洋/北极太平洋对流层环流的变率，其设计目标是追踪阿留申低压与波弗特高压中心的相对位置关系，精准反映前者的强度与位置，以及后者相关的经向偶极子特征。该指数的优势在于其对北太平洋向北极的平流事件，以及环流型如何引导该平流过程具有较高敏感性。该指数既能反映北太平洋指数（North Pacific Index，NPI）的变率，也包含跨阿拉斯加、经白令海峡向北输送，以及覆盖东西伯利亚海、楚科奇海、波弗特海区域的平流特征信息。截至目前，该指数已被用于评估北太平洋与北极太平洋区域季节性冰冻圈相变时间、生态系统物候的年际变率，以及白令海海冰扩张/消融和气溶胶输送事件的次季节变率。本系列的首份数据集以欧洲中期天气预报中心第五代再分析资料（ECMWF Reanalysis v5，ERA5）为数据源，计算时段为1940年1月至2025年5月（详见研究方法）。我们计划每年6月左右定期更新该数据集，以补充最新一年的观测数据——鉴于该指数在9月至次年5月期间的应用价值最高。